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Chemical Engineering vocabulary · Fluid Flow, Pumps and Piping

Reynolds number

Meaning in chemical engineering, with examples

/ˈrɛnəldz ˌnʌmbər/nounCommon term

In chemical engineering, Reynolds number means: A dimensionless number (Re = ρvD/μ) that compares inertial forces with viscous forces and tells you whether flow is laminar or turbulent.

In Turkish: Reynolds sayısı

How it is used

Used in pipe flow, heat transfer and mixing calculations. In pipes, flow is usually laminar below about 2,100–2,300 and fully turbulent above about 4,000. Engineers calculate Re first, then pick the right friction factor or heat transfer correlation.

Example sentences

  1. With this oil the Reynolds number is only 900, so the flow is laminar.

  2. Keep the Reynolds number above 10,000 in the tubes for good heat transfer.

Common collocations

  • calculate the Reynolds number
  • high Reynolds number
  • pipe Reynolds number
  • impeller Reynolds number
  • laminar flowSmooth flow in which fluid moves in parallel layers with little mixing between them. In pipes it happens at low Reynolds numbers, typically below about 2,100.
  • viscosityA fluid's resistance to flow: honey has a high value, water a low one. Measured in pascal-seconds or, more often in practice, centipoise (cP).
  • pressure dropThe loss of pressure as a fluid flows through a pipe, valve, filter, bed or piece of equipment, caused mainly by friction.
  • heat transfer coefficientA number that shows how easily heat passes from one fluid to another through a wall, measured in W/(m²·K). The higher it is, the smaller the exchanger can be.

More terms: Fluid Flow, Pumps and Piping

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